This invention relates to improved explosive slurries. More particularly, the invention relates to thickened explosive slurries of the type containing an oxidizing salt, an organic fuel, aluminum, a thickening agent, and water.
Aqueous explosive slurries are well known in the explosives art and have been widely accepted by users of commercial explosives. Such explosives generally contain a wide variety of ingredients. For instance, a slurry usually contains an inorganic oxidizing salt such as ammonium nitrate or an alkali or alkaline earth metal nitrate, e.g. sodium nitrate, potassium nitrate, calcium nitrate, etc., corresponding perchlorate salts, or mixtures thereof. Organic fuels are also utilized in such slurries. Suitable organic fuels include a large variety of finely divided non-explosive carbonaceous materials such as carbon black, ground coal, fuel oils, vegetable oils, wax, wood pulp, vegetable pulp, sugar, nut meal, bagasse, etc. The explosive power and sensitivity of explosives is further enhanced by the use of a metallic fuel. Such fuels include finely divided light metals and light metal alloys, e.g. aluminum, magnesium, boron, etc., and alloys thereof.
Depending upon the type of blasting agent desired, explosive slurries may optionally contain high explosive ingredients. Such ingredients include, for instance, the highly explosive materials, nitrostarch, trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), nitrocellulose, cyclotrimethylene trinitramine (RDX) and mixtures thereof. Slurries containing explosive ingredients are generally more powerful and more sensitive to detonation than those which to not contain such ingredients.
Aqueous explosive slurries are advantageously thickened or gelled. Thickening serves to prevent segregation of the ingredients, to prevent leaks from containers having small perforations, to inhibit evaporation of liquid ingredients, and to provide resilient products when filled into elastic casings. The slurries are conventionally thickened with water-soluble polysaccharides, e.g. carboxy methyl cellulose, natural starches, and gums. Galactomannan gums, particularly guar gum, have been preferred for this purpose. Such gums cause slurries to gel if employed in sufficiently high concentrations, and cross-linking agents such as polyvalent inorganic salts, e.g. sulfate, nitrate, chromate, or chloride salts of chromium, iron, aluminum, zinc, potassium, or tin or a water-soluble pentavalent antimony compound, such as potassium pyroantimonate, may be added to enhance gel formation.
Although aqueous explosives have found wide acceptance and have many advantages over other types of explosives, their manufacture presents certain unique problems. One such problem has been that slurries tend to lose sensitivity to detonation upon mixing. Although the exact cause of this loss of sensitivity is not known, one theory is that it is the result of mechanical removal of air bubbles which are normally present on the surface of the particles of the metallic fuel. Accordingly, a need exists for a means for maintaining the sensitivity of explosive slurries during mixing and filling operations.